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Moon by Simaudio Neo 340i integrated amplifier

By Herb Reichert • Posted: Mar 3, 2016

August 26, 1944: The liberation of Paris. Imagine ranks of tattered Canadian soldiers marching

past the Moulin Rouge à Paris. The voice of Édith Piaf singing "Ou sont-ils, mes petits

copains?" (Where are my boyfriends?). Maurice Chevalier crooning "Ça sent si bon la France"

(It smells so good in France). A Canadian army tank with the words Kaput and Finito painted in

white above the word Montréal, motoring past the Eiffel Tower. Remember the fresh,

celebratory taste of fine Champagne.

This was the place, the mood, the reverie with which I began my examination of Simaudio's

Moon Neo 340i integrated amplifier. Why? Because Canada's contributions to the Allied Forces

and to perfectionist audio are underappreciated. Because French is the official language of

Boucherville, Quebec, where Simaudio Ltd. has its factory. And because Paris and Canada are

two of the places I have most visited, most explored, and most loved—in real life, in memories,

and in dreams.

The first song I remember playing through the Moon Neo 340i was "Paris," sung by Piaf

on Edith Piaf (LP, EMI/Music for Pleasure MFP 5046). The sound of the barrel organ and

accordion accompanying The Little Sparrow seemed so tangible and direct that it took my mind

immediately to Montmartre: to cobblestones, dancing poodles, and organ grinders. Even before

Piaf began singing, I recognized the Neo 340i's exceptional ability to dig straight through to the

microphone(s) and recording venue. I knew immediately that listening to the Neo would be like

drinking Bollinger Grande Année Brut 2002 ($120/750ml).

Along with the Neo, I was using a Pioneer PLX-1000 turntable with Ortofon 2M Black cartridge,

and Magnepan .7 loudspeakers. When la grande Piaf whispered into the mike as a drum tap-

tap-tapped in the distance behind her, I locked in completely: In my mind, the dark space

between the édith and the drum was charged—with dim light, dust, and smoke. I could sense

the height of the drum from the hard floor.

I was listening to a performance recorded in 1949!

That, my dear readers, is the nature of this vivid French studio recording, the diminutive French

songbird, and the sparkling brut clarity provided by the Moon Neo 340i driving the Magnepan

.7s.

Description

One reason the Magnepan .7s played so well with the Simaudio integrated is that Magnepan

speakers prefer amplifiers that double their rated output into 8 ohms when presented with a 4-

ohm load—as does the Neo 340i, which is specified as producing 100Wpc into 8 ohms or

200Wpc into 4 ohms. The Maggies' infamous hunger for current was satisfied by the 340i's

ability to continuously deliver up to 30V at 12 amps, with 22-amp peaks. The Neo 340i uses four

bipolar transistors per channel, operated in class-A for the first 5W, and in class-AB for all

subsequent joules per second.

I am a slow-working audio reporter. I need months—sometimes a year—to get a proper feel for

a product. This is especially true with integrated amplifiers, because today's models can be

heavily laden with features, each of which takes time to appreciate. The Moon Neo 340i has

been in and out of my system for more than a year—so long that I had to upgrade its DAC and

firmware to finish this review. The basic 340i, without phono stage or DAC module, can be had

for $4700. Later, you can add a moving-magnet/moving-coil phono stage ($400) and/or a DSD

DAC ($900). That's $6250 for Lune Ö la carte. Or you can buy a 340i that includes all of these

options—Simaudio calls the package the D3PX—for $5800. Simaudio sent me the D3PX

edition.

The Moon Neo 340i D3PX is a textbook example of a contemporary, top-quality, full-featured

integrated amplifier. On its backside are four analog RCA inputs, one of them dedicated to the

phono board, and four digital inputs: TosLink, two S/PDIF RCAs, and USB. There are two line-

level (RCA) analog outputs: one fixed, the other variable. Standard features on all Neo 340i

amps include: SimLink, to provide two-way communication among various Simaudio Moon

components, including the MiND streamer; a 12V trigger; a RS-232 port for custom installation,

bidirectional feedback, and firmware updates; and an IR port for external control.

On the Neo 340i's classy-looking signature faceplate are a ¼" headphone jack and a 1/8" Media

Player (MP) input jack. Just above those are two buttons: Spk Off, which turns off the output

signal to the speakers when you're using headphones; and Mute, which switches off the output

signal to everything, including the fixed and variable RCA outputs.

To the left of the central, red-lit display is a cluster of five buttons. At the top is Standby, which

disengages the input section from the remainder of the 340i's circuitry, though all circuits remain

powered up. Just below that are buttons to engage the MP input and to turn the display off and

on, and below those are two more, for toggling between input options.

Page 14 of the Neo 340i's manual is dedicated to the operation of its remote control. At the

bottom, it states: "NOTE: The buttons labeled don't affect the operation of the 340i."

Immediately, I knew: Simaudio has done this only to annoy me. Boooo! Hiss! Grrrr!

With speakers: Magnepan .7

The more I use the Magnepan .7s ($1400/pair), the more I love them. Their extraordinary

imaging, sweetness of tone, and down-to-earth naturalness are the antitheses of all things

mechanical and "hi-fi." I believe that they are among the best speakers available today, at any

price. The planar-magnetic, flat-panel .7s do what stand-mounted box speakers don't: They

move copious amounts of air. Each speaker has 400 square inches of driving surface—eight

times more than an 8" woofer, and more than 16 times as much as a 5.5" mid/woofer like the

one in KEF's LS50. Moving that much air energizes a small room like mine in a way that lets me

really feel the sound. Bass may not go very low, but it's present in the room with me, touching

me physically. Little boxes can give the idea of bass—a simulacrum—but never bass that

touches your skin. The Magnepan sound is always more tactile, more of the senses, than what I

experience with little box speakers, whose sound is always more of the mind.

When I used the Moon and the Maggies to listen to my swamp-blues buddy Slim Harpo sing

"I'm a King Bee" and "Rainin' in My Heart," from his first album, Slim Harpo Sings "Raining in My

Heart . . ." (LP, Excello LP-8003), my room felt awash with rich, pulsing molecules of bass and

midrange energy. The high frequencies were vaporous, but precise and wonderful. The

Simaudio's apparent speed and transparency tamed the Magnepans' inherent sweetness to the

point where the .7s began to sound like the high-resolution transducers they are. The reverb

added to Harpo's seductive voice in this 1961 recording had an enticing presence of its own.

Music emerged with such clarity and ease that I became relaxed and happy. This deeply

satisfying amp-speaker pairing reproduced all types of music with charm and authority.

With speakers: Technics SB-C700

The fast, neutral sound of the Moon Neo 340i was enhanced by the low-distortion naturalness

of Technics' SB-C700 stand-mounted minimonitors that I reviewed in January. I played Claude

Debussy playing Claude Debussy, with soprano Mary Garden, from Claude Debussy: The

Composer as Pianist: 18 selections recorded for M. Welte & Sons in Paris, in 1904 and 1913

(CD, Pierian 0001). I have revered this disc, and Debussy's unusual pianism, ever since its

release, in 2000. The Moon and Technics have now made it my new religion.

This supremely crafted Welte-Mignon piano-roll recording was made using a finely tuned and

restored Feurich-Welte piano playing laboriously rerecorded rolls from the collection of Dick and

Helena Simonton, recorded in stereo using two Neumann KM 83 microphones. The results of all

this love and labor are a stupefyingly real AAD recording that appears to capture every nuance

of the French master's touch, pedaling, and expression. Debussy's deliberateness, hesitancy,

and eccentric tempos in his La cathédrale engloutie seem more flesh-and-blood soulful than

most pianists now living can muster on their best day at the keyboard. The Welte-Mignon

recording piano

even captured

Debussy's half-

pedaling!

This was another

deeply satisfying

combination of

amplifier and

speakers.

Phono Stage: Moving-magnet

If I could revive Josef Hofmann or Ignace Jan Paderewski, how close to their pianos would I like

to sit? After a lifetime of wondering, I have concluded that I like close: front-row close. I want to

see the pianist's knees move as he works the pedals. I want to hear the felts and keys returning

to rest. I enjoy the affective reality of the player working the whole instrument. Which is exactly

what I experienced listening to and watching, from the second row, Keith Jarrett at Carnegie

Hall. I was staring up at Jarrett's knees and the bottom of the soundboard. I watched his feet

stomp from about 30' away. This intimacy let me experience his playing with my entire body. His

wayward affectations drew me in much better than if I'd been sitting in a balcony box.

Listening at home, I desire that same intensity and artistic presence. Happily, I received a nice

measure of it when listening to Jarrett's Concerts Bregenz München (3 LPs, ECM-3-1227). I

couldn't see Jarrett's knees, but I could hear his head and voice moving above the keyboard. I

could hear his shoes on the pedals.

Vicissitudes of Power

The aspect of recorded music that is most affected by preamplifiers and power amplifiers is its

viscosity—ie, how thick or thin or transparent the music sounds. This in turn affects grain,

contrast structure, and, especially, musical flow. The perceived viscosity or plasticity of an audio

amplifier's sound lies typically in its internal impedances, time constants, bandwidth, and voltage

plus current capabilities. Musical viscosity also depends on the designer's choice of resistors,

capacitors, regulators, and transformers.

I mention all this because it sounded to me that the Simaudio design team has made some

sophisticated viscosity-oriented design choices that have resulted in audio products, like the

Moon Neo 340i, of unique transparency and fluidity.

Phono Stage: Moving-coil

I change phono cartridges often. Therefore, I'm always happy when an integrated amplifier

includes choices of gain (40 or 60dB) and loading (100 ohms or 47k ohms plus 0pF or 100pF),

as does the Moon Neo 340i D3PX. Simaudio uses active circuitry—as opposed to

transformers—for the extra gain.

Unlike most phono stages, in which choices of amplifier gain and cartridge loading are made

with little switches or buttons, the Neo 340i's phono stage requires that you (or your dealer)

remove the amp's top plate and reposition separate right- and left-channel jumper blocks for

each choice. I know, it sounds tricky, maybe even dangerous—but it's not. It's simple, almost

foolproof, and explained very clearly in the manual. The whole procedure took me less than 10

minutes, and its simplicity gave me the opportunity to experiment and be fickle.

Most important, the results were worth the effort: The sound quality of the 340i's $400 phono-

stage option (less, of course, if it's ordered as part of the entire D3PX package) is so ridiculously

good that I doubt most users will ever want further upgrades. If they do, Simaudio's Moon

Evolution line offers three standalone phono stages, the 310LP ($1800), 610LP ($7500), and

810LP ($13,000).

My only complaint: My Zu Denon DL-103 cartridge was not perfectly happy with the Neo 340i.

The Zu's 40-ohm impedance plays more naturally and in a more relaxed manner into 470 or

1000 ohms than into either of the 340i's choices of 100 ohms or 47k ohms. Into 47k, the Zu was

too uptight.

Meanwhile, the 6-ohm internal resistance of my Jasmine Turtle cartridge was more than happy

with the Neo 340i's 100-ohm setting. It played stronger, cleaner, and with more detailed bass

than it had with any other phono stage I have in the bunker. (My review of the Turtle moves

slowly forward . . . )

DSD DAC

Last July, Simaudio introduced an upgrade for the Moon Neo 340i's DAC that improved on what

I'd already felt was the 340i's strongest asset. My review sample's original DAC was fast and

sure, open and clear, with bass that played exactly as it should. But compared to my reference

D/A converter—Halide's DAC HD ($495), which always sounds warmly detailed, juicy, and

alive—the Neo 340i's original DAC sounded a bit brisk and chilly, like a cloudless November

day. The new DSD DAC demonstrated increases in neutrality and materiality, and felt a bit

bolder, yet more at ease.

I believe strongly in the importance of high-end audio dealers. The future and quality of our

sacred hobby rests squarely on their shoulders. If you buy an amp or speaker on the Internet

and it sounds bad in your listening room, you have no one to blame but yourself. Worse, you

have no one who cares, or wants to help you. But high-end audio salespersons are there to be

exploited as teachers, oracles, lifestyle consultants—and maybe even friends.

I mention this because I did not feel confident in my ability to install the 340i's new DAC board

and do the necessary firmware upgrade. So I took my review sample to the charming and

knowledgeable Michael Toto, of New York's famous Stereo Exchange. The upgrade process

began with his welcoming smile, included a lot of impassioned jabber about headphones, amps,

and speakers, and ended with my satisfied grin and a handshake. Dealers rule!

Headphones

Like a hooded monk with an inkwell, I spend my days sitting at a desk, writing and imagining.

My hood is a pair of headphones—I listen to Tidal, and play my diverse collection of files

downloaded from HDtracks. I enjoy the LSD intensity of listening through high-quality

earspeakers. I find that headphones force my ADHD mind to focus—and remain focused—

better than do speakers en l'air ouvert. For several months now, Simaudio's Moon Neo 230HAD

headphone amplifier ($1500 with DAC) has been firmly ensconced in my desktop reference

system. While the 230HAD plays with a tighter, breathier, and punchier authority than the 340i's

headphone output, the 340i exhibits a similar (but more softly-focused) clarity that flatters the

female voice more than the male.

Through the 340i and AudioQuest NightHawk headphones, I'm now listening to "High on a

Mountain," from the New Appalachians' From the Mountaintop (24-bit/192kHz, Chesky). This

bluegrass standard by Ola Belle Reed is such a mournful lament—"High on a mountain

standing all alone / wondering where the years of my life have gone"—that it chokes me up

every time I play it. The luminous recording of this group—which features the girl I want to run

away with, singer Noah Wall—is a potent mix of musical and recording artistry. With the 340i

headphone stage, I felt like Noah Wall was standing directly in front of me; I could have reached

out and touched the mandolin and violin players with my left and right hands respectively.

Chesky's binaural imaging was accurately described, but the roadhouse punch was missing.

With the Audeze EL-8s, the plucked bass was soft and overly warm. Wall's vocals were nicely

textured but less "in-the-room" than with the 230HD. The highs were sometimes quite attractive

and non-fatiguing—but neither precise nor extended.

Unlike the 340i's phono stage and DAC, which are extraordinary enough to satisfy over the long

haul, I suspect most high-end headphone junkies will feel the need for a better-quality

headphone stage. If so, Simaudio is ready: the 230HD ($1500 w/DAC) and 430HA ($3500–

$4300) would be natural choices.

Comparison: Rogue Audio Sphinx

As I have with the Magnepan .7s, I've been constantly rediscovering how just how much I love

Rogue Audio's Sphinx integrated amplifier, the very first product I reviewed

for Stereophile in August 2014. Folks, this baby jumps, thumps, and sings as it has no right to

for $1295. But the Moon Neo 340i showed me exactly what I should expect for not quite four

times the Sphinx's price: The Neo 340i delivered levels of microdetail, refined transparency, and

mercuric nimbleness the Rogue can only hint at. The Moon described a recorded soundspace

with the kind of tactile precision delivered by only the most expensive amplifiers. While the

Sphinx plays the lowest octaves with masterful ease, the Neo showed me bass notes in full—

unblurred and ungeneralized, from start to finish.

Comparison: Hegel Music Systems H160 and Line Magnetic LM-518IA

The Hegel Music Systems H160 ($3500) is a bold mountain climber of an integrated amplifier.

Well trained and strong, it conquers your speakers with adolescent eagerness. But! The H160

plays music with a kind of bourgeois moderation that makes me yearn for a more bohemian

libidinousness. Similarly, the Simaudio Moon Neo 340i's well-manicured precision made me

wish for an occasional taste of slutty voluptuousness. On those days, I switched to the Line

Magnetic LM-518 IA ($4400). Neither the Hegel nor the Simaudio could match my Line

Magnetic for brilliant Van Gogh colors, verdant textures, or riotous debauchery.

60% pinot noir, 40% chardonnay

While it plays music beautifully, it's unlikely that the Simaudio Moon Neo 340i integrated

amplifier was created for the inexperienced audiophile. Its virtues are substantial and varied, but

much of its wonderfulness is subtler than my descriptions suggest. The character of its lively

sound was strong—but a quiet strength. None of its charms jumped out and mugged me. It

danced and sang well, but at its core, the Neo 340i was really about refinement and

consistency. Through it, music sounded fresh and subtly articulated, always in good balance

and proportion. Like Marantz's classic tube gear, which it resembled in sound and appearance,

this integrated amplifier was created for audio cognoscenti—those who know how rare a really

well-engineered amp actually is. For these reasons, I believe the Moon by Simaudio Neo 340i

will hold its value: The way it satisfied this listener with its Champagne Brut audio aesthetic

should never go out of fashion. Confidently recommended.

Description: Solid-state integrated amplifier. Analog inputs: 1 XLR, 4 RCA, 3.5mm Media

Player. Optional digital inputs: optical, 2 coaxial, USB. Optional phono inputs: 47k ohms input

impedance (moving-magnet), 100 ohms or 47k ohms input impedance (moving-coil). Analog

outputs: fixed, variable (both RCA). 1 pair speaker outputs. Headphone output: 0.25" phone

plug. Rated output power: 100Wpc into 8 ohms (20dBW), 200Wpc into 4 ohms (17dBW).

Dimensions: 16.7" (429mm) W by 3.5" (89mm) H by 14.7" (376mm) D. Shipping weight: 28.6

lbs (13kg).

Finishes: Black standard; Silver, Two-Tone available via special order.

Serial number of unit reviewed: 07022324.

Price: $4950. Options: MM/MC phono stage, $400; DSD DAC, $900; D3PX edition (all options

included), $5800. Approximate number of dealers: 80. Warranty: 10 years.

Manufacturer: Simaudio Ltd., 1345 Newton Road, Boucherville, Quebec J4B 5H2, Canada.

Tel: (450) 449-2212. US: Simaudio Ltd., 2002 Ridge Road, Champlain, NY 12919.

Web: www.simaudio.com.

Associated Equipment

Analog Sources: Pioneer PLX-1000 turntable, Ortofon 2M Black cartridge; Thorens TD 124

Mk.I turntable, Abis SA 1.2 tonearm, Zu Denon DL-103 or Jasmine Turtle cartridge; Technics

SL1200 Mk.2 tonearm, SME M2-9 tonearm, Soundsmith Carmen or Shure SC35 cartridge; VPI

Scout Jr. turntable, Ortofon 2M Red cartridge.

Digital Sources: Onkyo Integra DPS-7.2 disc player, Halide DAC HD DAC.

Preamplification: Intact Audio step-up transformer; Blue Horizon Ideas Profono, Schiit Audio

Mani phono stages.

Integrated Amplifiers: Hegel Music Systems H160, Line Magnetic LM-518 IA, PrimaLuna

ProLogue Premium, Rogue Audio Sphinx.

Headphone Amplifiers: Audeze Deckard, Linear Tube Audio microZOTL, Schiit Audio Asgard,

Simaudio Moon Neo 230HAD.

Headphones: AKG K812, Audeze EL-8, AudioQuest NightHawk.

Loudspeakers: Dynaudio Excite X14, Falcon Acoustics LS3/5a, KEF LS50, Magnepan

.7, Technics SB-C700.

Cables: Speaker: AudioQuest Type 4, Auditorium 23, Kimber Kable 8TC. Interconnect:

AudioQuest Big Sur & Cinnamon & Golden Gate, Auditorium 23, Kimber Kable Silver Streak.

Accessories: Sound Anchor stands, Moongel stylus cleaner, Dr. Feickert Analogue cartridge-

alignment protractor.—Herb Reichert

Measurements

I performed a full set of measurements on the Simaudio Moon Neo 340i using my Audio

Precision SYS2722 system (see the January 2008 As We See It"). I looked first at the behavior

of the optional digital-input board, using either S/PDIF data sourced from the Audio Precision

via optical or coaxial links, or USB data from my Mac Book Pro running on battery power. To

avoid overloading the power-amplifier section, I switched the loudspeakers off and looked at the

signals at the fixed line-output jacks. The TosLink input locked to data with sample rates up to

96kHz, the coaxial inputs to data sampled at all rates up to 192kHz. Apple's AudioMIDI app

revealed that the Neo 340i operated with 32-bit integer data at all sample rates from 32 to

384kHz. The USB Prober utility identified the Simaudio as the "MOON USB DSD HD Audio"

from "Simaudio Ltd.," and confirmed that its USB input operated in the optimal isochronous

asynchronous mode.

The digital input preserved absolute polarity (ie, was non-inverting) at both the line and speaker

outputs. A 1kHz tone at 0dBFS gave rise to a level of 1.89V at the line output, though with the

volume control set to its maximum, digital data at –12dBFS resulted in a level just below

clipping. The impulse response with 44.1kHz data (fig.1) revealed that the Neo 340i's

reconstruction filter was a conventional FIR type with a sharp rolloff above 20kHz with 44.1kHz

data (fig.2, red and magenta traces). The aliasing product of a full-scale tone at 19.1kHz at

25kHz (blue and cyan traces) is suppressed by 85dB, and the harmonics of the fundamental

tone are all very low in level.

Fig.1 Simaudio Moon Neo 340i, S/PDIF input, impulse response, 44.1kHz data.

Fig.2 Simaudio Moon Neo 340i,

S/PDIF input, wideband

spectrum of white noise at –

4dBFS (left channel red, right

magenta) and 19.1kHz tone at

0dBFS (left blue, right cyan),

with data sampled at 44.1kHz

(20dB/vertical div.).

Fig.3 shows the digital module's frequency response with data sampled at 44.1, 96, and

192kHz. There is a slight imbalance between the channels, but the responses follow the same

basic shape, with a sharp rolloff just below half of each sample rate. With 384kHz data, the

response followed the same shape as the 192kHz traces, but with extended output above

96kHz, reaching –10dB at 160kHz. Channel separation via the digital inputs was excellent, at

105dB below 1kHz and still 85dB at the top of the audio band. Noise levels were also low for

digital input signals, so that increasing the bit depth from 16 to 24 with dithered data

representing a 1kHz tone at –90dBFS dropped the noise floor by almost 20dB (fig.4), implying

resolution of at least 19 bits. Some low-level, supply-related spuriae are visible in this graph, but

overall the noise floor is sufficiently low that the Simaudio's reproduction of an undithered 16-bit

sinewave at exactly –90.31dBFS was essentially perfect (fig.5). With undithered 24-bit data, the

result was a well-formed sinewave (fig.6).

Fig.3 Simaudio Moon Neo 340i,

S/PDIF input, frequency response

at –12dBFS into 100k ohms with

data sampled at: 44.1kHz (left

channel gray, right green), 96kHz

(left cyan, right magenta), 192kHz

(left blue, right red) (0.5dB/vertical

Fig.4 Simaudio Moon Neo 340i, S/PDIF input, 44.1kHz data, spectrum with noise and spuriae of

dithered 1kHz tone at –90dBFS with: 16-bit data (left channel cyan, right magenta), 24-bit data

(left blue, right red) (20dB/vertical div.).

Fig.5 Simaudio Moon Neo 340i,

S/PDIF input, waveform of

undithered 1kHz sinewave at –

90.31dBFS, 16-bit data (left

channel blue, right red).

Fig.6 Simaudio Moon Neo 340i, S/PDIF

input, waveform of undithered 1kHz

sinewave at –90.31dBFS, 16-bit data (left

channel blue, right red).

As implied by the blue and cyan traces in

fig.2, the Simaudio's digital module

produced very low levels of harmonic

distortion, with the third harmonic the

highest in level, at just –106dB (0.0005%,

fig.7). Intermodulation distortion was

similarly low, and the digital module offered

superb rejection of word-clock jitter via both

its TosLink (fig.8) and USB inputs (fig.9).

Fig.7 Simaudio Moon Neo 340i, S/PDIF

input, spectrum of 50Hz sinewave, DC–

1kHz, at 0dBFS (linear frequency scale).

Fig.8 Simaudio Moon Neo 340i, S/PDIF input, high-resolution jitter spectrum of analog output

signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 16-bit data (left

channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.

Fig.9 Simaudio Moon Neo 340i, S/PDIF input, high-resolution jitter spectrum of analog output

signal, 11.025kHz at –6dBFS, sampled at

44.1kHz with LSB toggled at 229Hz: 24-bit

data (left channel blue, right red). Center

frequency of trace, 11.025kHz; frequency

range, ±3.5kHz.

The optional phono stage offered 39.65dB

of gain measured at the fixed line-output

jacks when set to MM (moving magnet),

57.65dB of gain when set to MC (moving

coil). With the volume control set to its

maximum and the phono stage set to MC,

a 1kHz tone at 1mV resulted in a level of

4.56V at the speaker outputs; ie, a total

gain of 73.2dB. The phono module

preserved absolute polarity in both MM and MC modes, and the input impedance at 1kHz was

46k ohms at 1kHz when set to "47k," or 101 ohms when set to "100." The input impedance at

the frequency extremes was not appreciably different from that at 1kHz. (For these

measurements, the input capacitance was set to "0pF" for both modes.)

The RIAA error was very small (fig.10), though the right channel was very slightly higher in level

than the left. Both channels featured a low-frequency response that was down by 3dB at 20Hz.

Channel separation via the phono inputs was good, at >60dB, and the unweighted, wideband

signal/noise ratios were also good, at 78dB (MM, ref.1kHz at 5mV) and 61dB (MC, ref. 1kHz at

500µV), both measured with the input shorted. The A-weighted ratios were even better, at a

respective 86.5 and 75.3dB. (All figures are the average of the two channels.)

Fig.10 Simaudio Moon Neo 340i, phono input, response with RIAA correction (left channel blue,

right red) (1dB/vertical div.).

At normal levels, the 340i's phono

module offered very low levels of

harmonic distortion (fig.11) and

intermodulation distortion (fig.12).

However, while the overload margins

were very high at low and middle

frequencies, at at least 25dB (MM) and

29dB (MC), these dropped at 20kHz to

just 7dB (MM) and 11dB (MC). (All

figures referred to 1kHz at

Fig.11 Simaudio Moon Neo 340i, phono input, spectrum of 1kHz sinewave, DC–10kHz, at 1V

into 100k ohms (linear frequency scale).

Fig.12 Simaudio Moon Neo 340i, phono input,

HF intermodulation spectrum, DC–30kHz,

19+20kHz at 1V peak into 100k ohms (linear

frequency scale).

The amplifier as a whole offered a moderate

35.2dB of gain at 1kHz into 8 ohms for both

its balanced and unbalanced line-level inputs,

and both sets of inputs preserved absolute

polarity. While the balanced input impedance

was high, at 44k ohms at all audio

frequencies, the unbalanced input impedance

was relatively low, at 7200 ohms at 20Hz and 1kHz, dropping to just 5200 ohms at 20kHz. (The

input impedance was specified as 11k ohms

in the online version of the manual, but 22k

ohms in the printed manual that

accompanied the review sample.) As a

result, a tubed source with a high output

impedance at low frequencies might sound a

little lean.

The output impedance at the line-output

jacks was a low 100 ohms at all audio

frequencies. Measured at the speaker

outputs, it was a very low 0.05 ohm at low

and middle frequencies (including the series

resistance of 10' of speaker cable), rising inconsequentially to 0.08 ohm at the top of the

audioband. As a result, the modulation of the Neo 340i's frequency response by the Ohm's law

interaction between this impedance and that of our standard simulated loudspeaker was just

±0.09dB (fig.13, gray trace). The output was down by 3dB at a high 90kHz, meaning that a

10kHz squarewave was reproduced with short risetimes (fig.14), and there was no overshoot or

ringing. The 340i's frequency response was the same at all volume-control settings and for both

balanced and unbalanced inputs.

Fig.13 Simaudio Moon Neo 340i,

unbalanced frequency response

at 2.83V into: simulated

loudspeaker load (gray), 8 ohms

(left channel blue, right red), 4

ohms (left cyan, right magenta),

2 ohms (red) (0.5dB/vertical

div.).

Fig.14 Simaudio Moon Neo 340i, small-

signal, 10kHz squarewave into 8 ohms.

Channel separation for the line-level

inputs was an even 74dB R–L, but lower

at high frequencies in the other direction.

The unweighted, wideband S/N ratio,

measured with the inputs shorted to

ground but the volume control set to its

maximum, was a modest 71.2dB ref.

2.83V into 8 ohms, improving to 87.4dB

when the measurement bandwidth was

limited to the audioband, and to 90.2dB

when A-weighted. These figures were for the left channel; the right channel's ratios were all 2–

3dB smaller, due to there being a higher level of spuriae at 60Hz and its harmonics in that

channel (fig.15). These ratios and graph were taken with an unbalanced input; with a balanced

input, these spuriae were all up to 12dB higher in level, which I suspect is due to the fact that

these inputs are carried on a small board connected to the main board with flying leads.

Fig.15 Simaudio Moon Neo 340i,

unbalanced input, spectrum of 1kHz

sinewave, DC–1kHz, at 1W into 8 ohms

(linear frequency scale).

The Neo 340i's maximum power is

specified as 100Wpc into 8 ohms

(20dBW) or 200W into 4 ohms (17dBW).

Figs. 16 and 17 reveal that, with both

channels driven, the amplifier clipped at

130Wpc into 8 ohms (21.1dBW) and

200Wpc into 4 ohms, with low levels of

distortion at output powers of a few tens of watts. To be sure I was looking at true distortion, I

tested (fig.18) how the THD+noise percentage changed with frequency at 12.7V (equivalent to

20W into 8 ohms, 40W into 4 ohms,

or 80W into 2 ohms). Other than

into 2 ohms (gray trace), there was

only a slight rise in THD toward the

top of the audioband, and very little

increase into lower impedances.

Fig.16 Simaudio Moon Neo 340i,

THD+N (%) vs 1kHz continuous

output power into 8 ohms.

Fig.17 Simaudio Moon Neo 340i, THD+N

(%) vs 1kHz continuous output power into

4 ohms.

Fig.18 Simaudio Moon Neo 340i, THD+N

(%) vs frequency at 12.7V into: 8 ohms

(left channel blue, right red), 4 ohms (left

cyan, right magenta), 2 ohms (left, gray).

The distortion signature was

predominantly the subjectively innocuous

third harmonic (fig.19), though there was

also some second harmonic about 12dB

lower in level when the output power was

3dB below clipping into 4 ohms (fig.20),

as well as some lower-level, higher-order

harmonics and some supply-related

spuriae. When I tested the 340i with an

equal mix of 19 and 20kHz tones at a

level a few dB below visual clipping on

an oscilloscope, the second-order intermodulation product at 1kHz lay at just –96dB (0.0015%),

though the higher-order products at 18 and 21kHz lay at –74dB (fig.21).

Fig.19 Simaudio Moon Neo 340i, 1kHz

waveform at 50W into 8 ohms, 0.042%

THD+N (blue); distortion and noise

waveform with fundamental notched

out (red, not to scale).

Fig.20 Simaudio Moon Neo 340i,

spectrum of 50Hz sinewave, DC–

1kHz, at 100W into 4 ohms (linear

frequency scale).

Fig.21 Simaudio Moon Neo 340i,

HF intermodulation spectrum,

DC–30kHz, 19+20kHz at 100W

peak into 4 ohms (linear

frequency scale).

Finally, looking at the headphone

output, this offered the same

maximum gain as the speaker

outputs and was non-inverting.

However, as its source

impedance was a high 300 ohms,

the headphone output should be

regarded as utilitarian.

Overall, Simaudio's Moon Neo

340i offers excellent measured performance; I was particularly impressed by its affordably

priced phono and digital modules. One point should be noted, however: The 340i's heatsinking

isn't adequate for sustained use at high powers. Before the testing, when I preconditioned the

amplifier by running it at one-third power into 8 ohms with both channels driven—the worst case

for an amplifier with a class-B or -A/B output stage—its side-mounted heatsinks became too hot

to touch after 30 minutes, measuring 160.6°F (71.6°C). Even the top panel was hot, at 111.6°F

(41.1°C). This amplifier needs to be used in a well-ventilated location.—John Atkinson